Applying the principle of water decompositionover photoelectrochemical cells to heterogeneousphotocatalytic systems using powdered semiconductors isnow a field of great interest, encouraging new fundamentalinvestigations into chemical reactions which takeplace at the electrode surfaces in the electrochemicalcells. In the present review, we have focused on systems,which can convert solar energy into chemical energy byusing TiO2 photocatalysts. The photocatalytic decompositionof water under UV light irradiation has beenachieved with systems using various nanoparticle photocatalystssuch as TiO2. However, recently, visible lightresponsiveTiO2 thin films photocatalysts have beensuccessfully prepared by a radio frequency magnetronsputtering (RF-MS) deposition method. These thin filmphotocatalysts were found to have enough potential forthe separate evolution of H2 and O2 from water undersolar light. The TiO2 thin films were prepared on metalsubstrates by RF-MS deposition and mounted on H-typecontainers filled with water. This unique system enabledthe separate evolution of H2 and O2 from water undersunlight irradiation, opening new opportunities for thepractical on-site production of pure and clean H2 fromwater using abundant and clean sunlight in a safe,environmentally harmonious way.